One hundredth satellite earth
station installed in International
Monitoring System

The Provisional Technical Secretariat of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization is marking the installation of the 100th satellite earth station (VSAT) this week. VSATs – Very Small Aperture Terminals – are a key element in the Global Communications Infrastructure, which transmits data from the facilities of the International Monitoring System to the International Data Centre in Vienna. The International Monitoring System (IMS) is a global network of 337 monitoring facilities, which is being established under the terms of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) to monitor the Earth for evidence of a possible nuclear test explosion. The CTBT bans any nuclear weapon test explosion or any other nuclear explosion in any environment. The Global Communications Infrastructure (GCI) is the first global satellite communications network to be based on VSAT technology. Monitoring facilities and Member States in all areas of the world can exchange data via their local VSAT earthstations through one of three geosynchronous satellites. The satellites route the transmissions to hubs on the ground, and the data are then sent to the International Data Centre by terrestrial links. The GCI uses two additional satellites for more economical coverage of North America and Europe. The GCI is designed to be cost-effective, to operate with 99.5% availability, and to provide data within seconds from origin to final destination. As well as transmitting data from IMS facilities, the GCI is also used to distribute data and reports relevant to Treaty verification to States Signatories, in accordance with the Treaty provisions. The first VSAT was installed at the Vienna International Centre in 1998, and the first VSAT installed at an IMS facility was at the primary seismic station at Sonseca, Spain, also in 1998. Today, there are VSAT installations in every region of the world. The 100th installation is located in Namibia at the site of an infrasound and auxiliary seismic station. The Treaty was opened for signature on 24 September 1996 at United Nations Headquarters in New York. The Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization was established on 19 November 1996. It is assisted in carrying out its work by the Provisional Technical Secretariat, which is based in Vienna.

For further information on the CTBTO, please see or contact:
Annika Thunborg, Chief, Public Information  
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